The identity and topographic localization of infiltrating cells such as inflammatory and tumor cells and their products in patient specimens are analyzed by immunohistochemistry, in situ hybridization, polymerase chain reaction (PCR), microdissection and image analysis. Using these techniques we will make an accurate pathological assessment of disease from the studied tissue, guide an appropriate treatment for the patient, and understand the pathogenesis of the disease. In FY2001 we have continued and accomplished the following research: 1. Detection of Genes and Proteins in Primary Intraocular Lymphoma Cells. Using microdissection and PCR techniques we contiuned to detect IgH gene rearrangemnts and diagnose B-cell lymphoma in those cases of clinical manifestions but poor cytology. We detected the presence of DNA from several infectious agents including Toxoplasma gondii in primary intraocular lymphoma, but not normal cells in the eye. We speculated that infectious agents might play a role in some forms of primary intraocular lymphoma. In addition, we illustrated fluorescein angiographic findings in primary intraocular lymphoma. 2. New Pathology and Pathogenesis of Ocular Inflammation and Other Diseases. We detected T-cell receptor gene rearrangement and HTLV-1 gene in the infiltrating cells of retinal vasculitis caused by HTLV-1 infection. We reported conjunctival papillomas caused by human papilloma virus type 33. We demonstrated first time the loss of heterozygosity for the NF2 gene in retinal and optic nerve lesions of patients with neurofibromatosis 2. We reported noninvasive diagnosis and ophthalmic features of mucolipidosis type IV. 3. Experimental Models for Various Non-Inflammatory Ocular Diseases. We studied the role of chemokines in ocular inflammation. Using endotoxin-induced uveitis model (EIU), we showed the importance of MCP-1 in initiation of EIU. We also showed the involvement of apoptosis and gamma interferon in murine toxoplasmosis. In collaboration with investigators outside the NEI, we demonstrated that estrogen receptor repressor induced cataract formation (with D.L. Davis). Congenital nuclear cataracts and mild uveitis are observed in HIV-transgenic mice (with J.B. Kopp). These findings demonstrate that ocular pathology is an important manifestation of various systemic diseases.